Pollution can be defined as the introduction by man into the environment of substances that can adversely affect the health survival or activities of human and other living organisms. Pollutants are unwanted solid, liquid or gaseous chemicals produced as by-products or wastes when resource is extracted, processed, made into products or used. Pollution can also take the form of unwanted energy emissions such as excessive heat, noise or radiation. Alternatively, pollution has been expressed by Dix as one type of matter in a wrong place.
SOURCES OF ENVIRONMENTAL POLLUTION
Pollution can enter the environment by both natural
and human activities. For instance, volcanic activity and erosion by water are
natural processes and therefore inevitable sources of environmental pollution.
However, most natural pollution is dispersed over a large area and is often
diluted or broken down to harmless levels by natural processes. In contrast
most serious pollution from human occur in or near urban and industrial areas,
where large amount of pollutants is concentrated in small volumes of air, water
and soil.
Some of the pollutants that are added to the atmosphere include carbonoxides (C02, CO) largely generated from complete and incomplete
combustion of hydrocarbons in petrol engines, Volatile organic compounds or
hydrocarbons (HC) arising from combustion of fossil fuels and the oxides of
nitrogen and sulphur (NOx, SOx) are created by burning
fossil fuels particularly those containing sulphur. We also add suspended
particulate matter or solid particles like dust, soot, pesticides which include
polychlorinated biphenyls (PCBs) and many others. Heat produced when any kind
of energy is transformed from one form to another, noise produced by factories,
mines, motor vehicles, air planes, cassette players and many others pose a
source of environmental pollution.
EFFECTS OF ENVIRONMENTAL POLLUTION
The general effect of pollution produce deteriorating of the quality of
the environment. This means pollution is responsible for the dirty streams,
rivers and atmospheric contamination. Contaminated environment can have a
number of unwanted effects like damage to human health caused by some chemical
substances present in the air, food and water. Damage to plants and aesthetic
quality of the environment caused by smoke, chemical fumes, dust, dumping of
waste and dereliction. All these deleterious factors are affecting our
environment in which we reside, work and spend our leisure time.
Substances like carbon monoxide at high concentration, causes death in
human by blocking oxygen system in blood. SOx groups of pollutants
are highly destructive and very common in metal smelting and coal mining. These
also cause adverse chemical reactions to steel structures, power lines, some
roofing materials, many natural stones, cement and paints. Long exposure to high
noise levels can cause permanent hearing damage and similar exposure to dust
can damage lung tissue and in extreme cases cause premature death. Pollution
has many other effects on the environment some of which are irreversible.
ENVIRONMENTAL POLLUTION IN ZAMBIA
Africa has one of the fastest growing populations and the lowest
standard of living. The increasing human population will affect the environment
because more land will be needed for agriculture, shelter and recreation. The
vast population must be fed, clothed and provided with basic needs. To do this
government in Africa have to adopt chemical technologies which have deleterious
effects on the environment.
The percent annual population growth rate in Zambia is usually a threat
to the environment when the natural resources are reduced by the same
percentage. And this has been the case in Zambia for some years. The ability of
our environment to sustain us determines the future of our nation in social,
economic and political spheres. Environmental pollution has become serious in
Zambia with the development of modem industry in urban areas. The development
of harmful materials in the atmosphere and water sources are increasing and
people who are engaged in some special work are more likely to be hurt by pollutants.
1.
SOURCES OF ENVIRONMENTAL POLLUTION IN ZAMBIA
Zambia's main sources of environmental pollution are the many industries
in urban areas. Industrial activity in Zambia is mainly confined to areas of
Kafue and Copperbelt towns. In heavily industrialised areas, soil, water and
air have become polluted with deleterious effects on the biota.
It is well known fact that mining and smelting operations can be detrimental to the environment. The mining industry in Zambia is highly developed and has been identified as the chief polluter on the copperbelt where mining activities are concentrated. Most of the pollution by Zambia Consolidated Copper Mines (ZCCM) arises from the mining and processing of copper and cobalt at the smelters. The smelters are located in Kitwe, Mufulira and Luanshya. The Luanshya smelter is closed. Mining in Zambia has created serious environmental problems in localised areas. It is the main culprit for the environmental pollution in Kabwe, as found by Tembo, and on the Copperbelt. It emits large quantities of sulphur dioxide and particulate matter during processing of sulphur-bearing copper ore.
ZCCM Nkana division in Kitwe has an
acid plant where some of the sulphur dioxide is converted into sulphuric acid.
The excess is released into the atmosphere through the stacks. At Mufulira
division there is no acid plant and all the sulphur dioxide is discharged into
the atmosphere. Sulphur dioxide is also produced during the combustion of
fossil fuels (petroleum and coal) as these contain sulphur. The water effluents
from ZCCM concentrators contain suspended solids (mainly copper and cobalt)
which result in silt being deposited on the river bank. The amount of copper
and cobalt in suspended phase in the Kafue river were found to be 0.3 pg Co/L
and 462pg Cu/L at the municipal pump station in Chililabombwe before the river
enters the mining area. Downstream at the Kafue mission centre in Kitwe, the
amounts were found to be 3340pg Co/L and 3840pg Cu/L. The probable source of
the enrichment was the mining processes.
Occupational hazards are often encountered in mining and other working
environment. The major hazards arise from dusts, fumes and others. In Chingola
there is an open pit mine where workers are exposed to dust, Chilanga cement in
Lusaka and Ndola manufactures cement and is one of the major emitter of
particulate matter. Cement dust from cement kilns is released to the
atmosphere. Ndola Lime Company emits lime (calcium oxide) dust from kilns.
Ndola Lime and Lafarge cement are wrongly positioned in the eastern area of
Ndola instead of the west. Quarrying operations results in dust emissions.
These dusts are solid particles generated by handling, crushing, grinding and
disintegrating inorganic materials such as rocks, ore, metal and coal. Coal is
mined in Southern
Zambia at Maamba Coal mine by ZCCM. There are effects upon the lung
tissue and lung function resulting from inhalation and deposition of dust. The
exposure to man leads to respiratory diseases like silicosis from free
crystalline silica, talcosis from talc and others described as pneumoconiosis
with such dust as amorphous silica, coal dust and natural graphite involved.
Asbestos is widely used as a pipe and building material in Zambia.
Inhalation of asbestos fibres by workers has been known to produce asbestosis
with death from lung cancer as a sequel for many years. The sources of asbestos
in the air include processing and manufacturing of asbestos-containing
products. The people working in asbestos industries are at risk. Besides
asbestos fibres have been demonstrated in lungs of persons not occupationally
exposed but in the vicinity of the asbestos factory and asbestos mines. The family
members exposed to asbestos fibres brought home on the work clothes of asbestos
industry workers may accumulate lung fibre burdens similar to those seen with
occupational exposures and may be at risk for mesothelioma. In Kitwe, one of
the asbestos factory raised public concern over workers working without
protective materials. In USA asbestos is banned for use as water pipe, roofing
material etc.
Many other industries take part in environmental pollution in Zambia like Nitrogen Chemicals of Zambia (NCZ) in Kafue which produce sulphuric acid for use in manufacture of fertilisers. The process results in sulphur dioxide emissions. Nitrogen oxide (NOx ) is also emitted during the production of nitric acid and ammonia gas. These fertiliser nutrients are washed down the Kafue river where they enrich the river bed and feed the Kariba weed (a shrub) clogging up the river.
The untreated effluents from NCZ, Kafue
tannery, Municipal refuse etc. are released upstream into the river. The
domestic water is treated from biological point of view only, and not from the
chemical point of view. The effluents are diluted on entering the river. The
dilution is more during the rainy season and less in the dry season. Whatever
the season, the distance between municipal pump station and effluent release
point is very short, and the river does not have the capacity to clean the
water to safe levels.
Other potential polluters in Zambia may be dumping even more toxic
wastes running into ground and river water, like the pharmaceutical companies.
Textile industries like the Kafue textile which releases chemicals used during
dyeing processes. Bata tannery releases vast amounts of chromium during tanning
processes. Monarch Zambia Limited in Kitwe dumps zinc ash laden with lead from
galvanising process inside its premises. The petroleum sludge on the Copperbelt
has not been treated before release. Oil effluents from Indeni Petroleum
refinery in Ndola contaminates water in Kaloko and Munkulungwe streams.
HEAVY METAL POLLUTION
Heavy metals are natural components of the lithosphere and as such may
be found throughout the ecosystem. It has been known for several decades that
trace quantities of certain elements exert a positive or negative influence on
plant, animal and human life, Some elements are essential to life and nontoxic,
and hence non-polluting in certain formulations. Heavy metals, recognised as
highly toxic and dangerous pollutants, are placed only second to pesticides in
environmental importance. Metals are not
biodegradable, as a result they accumulate in vital organs of man and exert
progressively long term growing toxic actions.
1.
Spoil Heaps
Heavy metal pollution resulting from spoil heaps is usually a
consequence of insanitary habits. In urban areas, soil pollution is associated
with dumping on land of domestic refuse and solid resulting from the treatment
of sewage and industrial wastes. The soil is thus polluted with chemicals
including heavy metals and products of petroleum industries. These can reach
surface and ground water beneath and ultimately get incorporated into food
chain in the affected urban ecosystem. Water pollution usually severely damages
aquatic communities and, can cause immediate and long term harmful effects to
human life.
2.
Industrial Sources
Apart from smoke and fumes released from industries, the disposal of
industrial solid wastes constitutes a major source of environmental pollution
by toxic chemicals. These wastes have given rise to severe problems of soil
pollution either by poisoning the soil or crops or by eventual entry into
surface and ground water sources.
Mining of minerals involve removing of material from earth's crust and dumping on land of unwanted large masses of rock and waste material somewhere else, usually near mining site, resulting in slimes dams. Toxic substances leach out of such materials enter the soil and run off into streams and ground water. The processing of ores to recover economic mineral results in process effluent which contain suspended solids. Mining, therefore, has severe local, and sometimes regional, environmental impact on land, air and water.
Mining of
base metals or heavy metals result in gradual release to natural environment of
toxic substances of which the most important are metal ions and chemical
reagents. It is unusual for lethal concentrations to be released from a mine,
however the long term of exposure to sub-lethal doses are uncertain. Spoil tips
associated with non-ferrous mines contain anomalously high levels of heavy
metals compared with other environments. The table below shows some industrial
and agricultural sources of heavy metals in the environment.
Table 1.1:
Industrial and Agricultural Sources for Metals in the Environment Use Metal
Batteries and other electricals |
Cd~ |
Hg |
Pb |
Zn |
Mn |
Ni |
|
Pigments and paints |
Cd Cr |
Au A1 |
Pb As |
Zn Fe |
Ti Sn |
Hg |
Mn |
Alloys and Solder Biocides (pesticides, Herbicides preservatives) |
As |
Hg |
Pb |
Cu |
Sn |
Zn |
Mg |
Glass |
As |
Sn |
Mg |
Ca |
Na |
|
|
Fertilisers |
Cd |
Hg |
Pb |
A1 |
As |
Cr |
Cu |
Plastics |
Cd |
Sn |
Pb |
|
|
|
|
Textile |
Cr |
Fe |
A1 |
|
|
|
.... |
Fuel |
Ni |
Hg |
Cu |
Fe |
Mn |
Pb |
Cd |
Refineries |
...... Ni |
v |
Pb |
Fe |
Mn |
Zn |
|
Tannery |
...... Cr
|
A1 |
|
|
|
|
|
AIR POLLUTION
There are a range of atmospheric pollution problems currently
threatening the Earth’s general environment.
1.
Acid rain
This problem arises from the acidic gases produced by burning fossil
fuels in a number of different situations.
A summary of various atmospheric pollution problems caused by human activity. |
sulphur + oxygen → sulphur dioxide
S(s) + 02(g) → S02(g)
Oxides of nitrogen (NO+) (for example nitrogen dioxide, N02)
are also produced when air is heated in furnaces or in vehicle petrol engines.
These gases dissolve in rain water to produce ‘acid rain’.
There are numerous effects of acid rain, for example:
•
limestone buildings, statues, etc., are worn away.
•
lakes are acidified, and the presence of metal ions
(for example Al3+ ions) leached (washed) out of the soil damages the
gills of fish. The fish can die.
•
nutrients are leached out of the soil and from leaves.
Trees are deprived of these nutrients. Aluminium ions are freed from clays as
aluminium sulphate and damage tree roots.
The tree is unable to draw up enough water through the damaged roots,
and it dies.
The wind can carry acid rain clouds away from the industrialised
centres, causing the pollution to fall on other countries.
Remedies for the effects of acid rain are limited. Lime can be added to
lakes and the surrounding land, to decrease the acidity.
Air and Environmental Pollution |
2. Global warming and the ‘greenhouse effect’
The presence of water vapour, carbon dioxide (CO2) and other
gases in the air has served the planet well. The ‘trapping’ of heat by the atmosphere has kept the Earth warm.
Without this greenhouse effect, the average temperature of the Earth’s
surface would be -18°C, rather than 15°C. However, higher levels of certain
gases produced by human activity are increasing this heating effect and
producing global warming.
The ‘greenhouse gases’ that produce this warming include water
vapour, carbon dioxide, methane, the oxides of nitrogen and CFCs
(chlorofluorocarbons). These gases absorb heat from the Sun that is reflected
from the Earth’s surface. They prevent this heat from being re-radiated back
into space. So the Earth’s surface becomes warmer.
The greenhouse effect |
The levels of carbon dioxide released into the atmosphere are very high (about 5000 million tonnes per year). Large-scale deforestation, particularly of the tropical rainforests, to provide land for agriculture, also increases the level of carbon dioxide in the air because it removes trees j which absorb the gas for photosynthesis.
The effects of global warming are complex. The polar ice-caps would
begin to melt as the temperature rose. The increase in sea level would threaten
low-lying lands. Extensive climate change I is possible but is difficult to
predict. In some regions the effects may be good; but others may suffer long
droughts. There could be major shifts in desert and fertile regions. Tropical
storms could | increase in their intensity.
There is evidence, from dying corals to an increase in warm-water fish
in the North Sea, to show that global warming is taking place. Whether this is
due to increased carbon dioxide levels remains to be proved. Certainly the
concentration of CO2 in the Earth’s atmosphere has increased over
the last century (in 1850 it was 0.027%, and in 1993 it was 0.036%).
Ozone layer depletion
A protective layer of ozone in the stratosphere prevents harmful
ultra-violet radiation reaching the Earth’s surface. CFCs and other halogen
compounds are thought to cause the damage. International agreement has been
reached on restricting the use of these compounds (the Montreal Protocol). If
the situation were allowed to grow worse, exposure to higher levels of ultraviolet
radiation could cause more cases of skin cancer in humans, and cause damage to
crops.
There are various types of pollution that occur over smaller, local
areas. These usually occur in large cities, where there is heavy use of motor
cars. These forms of pollution are:
•
photochemical smog,
•
high levels of carbon monoxide, and
•
high levels of lead compounds.
Photochemical smog is formed in regions where there is a large amount of traffic. It was
first identified in Los Angeles, and forms only under certain conditions.
Severe photochemical smog often occurs in cities located in valleys, or
surrounded by hills or mountains. On sunny, windless days, oxides of nitrogen
are trapped by the hills in air that is close to the ground. A complicated
series of reactions takes place and ground-level ozone is one of the products.
In these circumstances ozone is harmful, particularly for asthma sufferers.
Carbon monoxide is the most common air pollutant in the industrialised world. It is
produced when hydrocarbon fuels are incompletely burnt. Carbon monoxide is
poisonous at levels of only 0.1%. Oxygen is very important to living things.
In our bodies it is carried round the body attached to haemoglobin in
our red blood cells. Carbon monoxide is attracted to haemoglobin over 200 times
more strongly than oxygen. In the blood, carbon monoxide prevents haemoglobin
from carrying oxygen. This leads to dizziness and headaches. Prolonged exposure
to carbon monoxide causes death.
Lead compounds are the most toxic heavy-metal pollutants in the air. Lead compounds
form part of the ‘urban dust’ that forms in a city atmosphere.
People living next to busy roads can have high levels of lead in their
blood. This has been linked with nervous disorders and with learning
disabilities in children. The increased moves to use unleaded petrol are
reducing this health hazard.
WATER POLLUTION
Water is another major resource that is essential to our life. However,
as with the atmosphere, we are continually guilty of polluting the rivers and
oceans. Industrial waste has been pumped into rivers in spite of legal
restrictions. Many pollutants are involved, but among the most dangerous are
the heavy metals such as cadmium and mercury. These can have disturbing effects
on living things even at very low levels. They can also pass from one living
thing to another along the food chain and affect life at various levels in the
chain.
Industries and power stations use water from rivers as a coolant. When
this water is returned to the river at a higher temperature, it causes thermal
pollution. Less oxygen can dissolve in this warmer water, so that
plants and animals in the water have greater difficulty breathing.
Sewage, detergents and run-off from fertilised fields can all reach
rivers and cause damage to plant and aquatic life. The beaches of Italian
resorts in the Adriatic have in the past been troubled by a green slime. This
slime was due to the flow of effluent (waste) from the delta of the river Po.
Sources of Water Pollution |
Pesticides also pose problems, as they can be concentrated through the food chain in fish. Apart from dangers to fish stocks, the concentration of possible cancer-causing chemicals at stages in the food chain is a source of great concern.
Pesticide chemicals can be concentrated in the food chain. |
POLLUTION IMPACT ON THE ZAMBIAN ENVIRONMENT
The environmental consequences of chemical emissions are a subject of
continuous debate. Some of the pollutants are a direct threat to the health of
people living in this exposed area.
Mining brings about noise pollution in three categories, these are fixed
plant, mobile plant (used internally) and external transport movement. Fixed
plant include equipment like crushers or processing machinery, loading
facilities and others. Mobile plant used on site is associated with drilling,
blasting and service operations. The other source of noise in mining is
external movements associated with all mining operations, the despatch of all
valuable products and waste and the movement of personnel. As stated earlier
long term exposure to high noise levels can cause permanent hearing damage to
people.
Soil is not only vulnerable to pollution by the mines but also to
several other industrial sources. Where commercial fertilisers have been used
over and over contamination of soil has taken place.
The use of pesticides does not solve pest problems but increases them by
killing beneficial species and building resistance in pests. Farming depends on
the quality and therefore the state of preservation of the soil. Our physical
development as human beings depends on the quality of what we eat and therefore
on the quality of farming.
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